Fix converted assets spawning without physics, and install the standalone importers by default

.github/actions/validate-kitless-image/action.yml

@@ -54,10 +54,8 @@ runs:
       print("ovrtx renderer initialized")
       '
 
-      # The Newton training probe is the shared one architecture CI also runs, so
-      # the command and its assertions live in one place. pytest goes only into
-      # this disposable layer; reinstalling the workspace would fail against the
-      # read-only source mount.
+      # Discover files by grep, not by pointing pytest at a directory: this image has no Isaac
+      # Sim, and collecting a directory imports every module to read its markers.
       docker run --rm --gpus all --network host \
         "${mount_args[@]}" \
         "$IMAGE_TAG" \
@@ -67,6 +65,8 @@ runs:
       python -m pytest \
         source/isaaclab/test/install_ci/misc/cartpole_training_smoke.py::test_train_cartpole_state_completes \
         source/isaaclab/test/benchmark/test_asset_suite_runtime_semantics.py \
+        source/isaaclab/test/sim/test_urdf_converter.py \
+        source/isaaclab/test/sim/test_mjcf_converter.py \
         -q -p no:cacheprovider
       '
 

docker/Dockerfile.kitless

@@ -46,12 +46,13 @@ COPY source/ source/
 COPY isaaclab.sh ./
 
 # Same entry point as Dockerfile.base. The selectors are explicit because a bare
-# --install excludes `ov` and `visualizer`; both take `[all]` here. The venv pins
+# --install excludes `ov` and `visualizer`; both take `[all]` here. `importers` carries
+# the standalone URDF/MJCF importers that replace the Isaac Sim ones. The venv pins
 # python3.12 to match the runtime stage's libpython3.12, and isaaclab.sh resolves
 # VIRTUAL_ENV first.
 RUN uv venv --python /usr/bin/python3.12 --seed --no-managed-python "${VIRTUAL_ENV}" \
  && chmod +x "${ISAACLAB_PATH}/isaaclab.sh" \
- && "${ISAACLAB_PATH}/isaaclab.sh" --install newton,rl[all],ov[all],visualizer[all] \
+ && "${ISAACLAB_PATH}/isaaclab.sh" --install newton,rl[all],ov[all],visualizer[all],importers \
  && python -c "import importlib.metadata as m; \
       names = {d.metadata['Name'].lower() for d in m.distributions()}; \
       assert 'isaacsim' not in names; \

docs/source/api/lab/isaaclab.sim.converters.rst

@@ -38,7 +38,7 @@ Mesh Converter
     :members:
     :inherited-members:
     :show-inheritance:
-    :exclude-members: __init__
+    :exclude-members: __init__, PhysicsVariant
 
 
 URDF Converter
@@ -53,7 +53,7 @@ URDF Converter
     :members:
     :inherited-members:
     :show-inheritance:
-    :exclude-members: __init__
+    :exclude-members: __init__, PhysicsVariant
 
 MJCF Converter
 --------------
@@ -67,4 +67,4 @@ MJCF Converter
     :members:
     :inherited-members:
     :show-inheritance:
-    :exclude-members: __init__
+    :exclude-members: __init__, PhysicsVariant

docs/source/how-to/import_new_asset.rst

@@ -25,8 +25,8 @@ use the Omniverse Kit to edit the asset and export it to other file formats. Isa
 these importers by default. They can also be enabled manually in Omniverse Kit.
 
 Isaac Lab's URDF and MJCF converter utilities first use the importer APIs from
-Isaac Sim when the full runtime is installed. In kit-less environments, install
-the standalone importer wheel as described in
+Isaac Sim when the full runtime is installed. In kit-less environments they fall back
+to the standalone importers described in
 :ref:`installation-standalone-importers` below.
 The Kit visualizer and GUI import dialogs still require an Omniverse Kit runtime.
 
@@ -43,25 +43,17 @@ For more details on instanceable assets, please check the Isaac Sim `documentati
 Standalone URDF/MJCF importers
 ------------------------------
 
-The URDF and MJCF converter scripts can run without Isaac Sim when the standalone
-``isaacsim-asset-isolated`` wheel is installed in the active environment. The wheel is not
-published on PyPI, so replace ``PACKAGE_INDEX_URL`` with the package index that hosts it:
+The URDF and MJCF converter scripts run without Isaac Sim. The standalone
+``isaacsim-asset-isolated`` wheel is a base dependency, so no extra install step is needed.
+Optionally pass ``--viz newton`` (or ``rerun`` / ``viser``) to preview the converted asset in a
+kit-less Isaac Lab visualizer:
 
 .. code-block:: bash
 
-   uv pip install "isaacsim-asset-isolated>=6.0,<6.1" \
-     --extra-index-url "PACKAGE_INDEX_URL"
-
-After installing the wheel, run conversion in the kit-less environment. Optionally pass
-``--viz newton`` (or ``rerun`` / ``viser``) to preview the converted asset in a kit-less
-Isaac Lab visualizer:
-
-.. code-block:: bash
-
-   python scripts/tools/convert_urdf.py \
+   uv run python scripts/tools/convert_urdf.py \
      path/to/robot.urdf path/to/output_dir --merge_joints
 
-   python scripts/tools/convert_mjcf.py \
+   uv run python scripts/tools/convert_mjcf.py \
      path/to/model.xml path/to/output.usd --merge_mesh
 
 If Isaac Sim is installed in the same environment, Isaac Lab uses the Isaac Sim importer

docs/source/setup/installation/index.rst

@@ -304,8 +304,8 @@ Install `uv <https://docs.astral.sh/uv/getting-started/installation/>`__ or
 
 ``-i`` always installs the core source packages. With no value, it also installs the optional
 ``mimic`` and ``teleop`` submodules plus the default Newton, RL, and visualizer dependencies.
-It does not install ``tetrahedralization``, ``contrib``, ``ov``, or Isaac Sim; request those
-explicitly when needed.
+It does not install ``tetrahedralization``, ``contrib``, ``ov``, or Isaac Sim;
+request those explicitly when needed.
 
 Use ``-i core`` for core packages only. Otherwise, pass a comma-separated list of selectors:
 
@@ -603,8 +603,8 @@ Extras can be combined freely: none of them conflict, so any set of extras -- in
 the Isaac Sim and OV backend stacks together -- resolves into a single environment.
 Use ``all`` to get every backend, RL library, and visualizer in one flag. The
 specialized extras (``rlinf``, ``mimic``, ``teleop``, ``tetrahedralization``, ``video``,
-``leapp``) and the developer ``test`` tooling are not part of ``all``; request them by
-name.
+``leapp``) and the developer ``test`` tooling are not part of ``all``;
+request them by name.
 
 .. isaaclab-uv-wheel-install::
 

pyproject.toml

@@ -47,7 +47,7 @@ dependencies = [
     "protobuf>=4.25.8,!=5.26.0",
     "hidapi>=0.14.0",
     "gymnasium>=1.2.0",
-    "trimesh",
+    "trimesh>=4.6.8",  # lower bound inherited from newton[importers]
     "pyglet>=2.1.6,<3",
     "transformers==4.57.6",
     "einops",
@@ -66,11 +66,15 @@ dependencies = [
     "pin ; platform_system == 'Linux' and (platform_machine == 'x86_64' or platform_machine == 'aarch64')",
     "pin-pink==3.3.0 ; platform_system == 'Linux' and (platform_machine == 'x86_64' or platform_machine == 'aarch64')",
     "daqp==0.8.5 ; platform_system == 'Linux' and (platform_machine == 'x86_64' or platform_machine == 'aarch64')",
-    # OpenUSD (kit-less mode). Both packages vendor a complete ``pxr`` runtime, so
-    # they must never co-install: usd-core supplies pxr where it has wheels (x86_64),
-    # usd-exchange supplies it on aarch64 (where usd-core has no wheel).
-    "usd-core>=25.11,<26.0 ; platform_machine == 'x86_64' or platform_machine == 'AMD64'",
-    "usd-exchange>=2.2 ; platform_machine == 'aarch64'",
+    # OpenUSD (kit-less mode). Use the same provider required by the URDF and MJCF importer
+    # packages so another complete ``pxr`` runtime cannot co-install with it. Two providers in
+    # one environment overwrite each other's files, and removing either then breaks ``pxr``.
+    # usd-exchange 2.3.0 vendors USD 25.5, matching the Isaac Sim 6.0 wheel stack.
+    "usd-exchange==2.3.0",
+    # Standalone URDF/MJCF importers, so conversion works without Isaac Sim. They install
+    # alongside it without displacing it: Kit serves ``isaacsim.asset`` from its extension
+    # roots when the runtime is present, and the standalone packages serve it otherwise.
+    "isaacsim-asset-isolated>=6.0,<6.1",
     # avoid broken hf-xet pre-release cached on NVIDIA Artifactory
     "hf-xet>=1.4.1,<2.0.0 ; platform_machine == 'x86_64' or platform_machine == 'AMD64' or platform_machine == 'aarch64'",
     # ----- tasks -----
@@ -87,9 +91,19 @@ dependencies = [
     # ----- newton (default physics engine) -----
     # Loose bound so the wheel co-resolves with isaacsim's newton[sim]==1.2.0 pin; the
     # exact git commit is forced via [tool.uv].override-dependencies (uv sync only).
-    # The importers extra carries the mesh-processing deps (coacd, fast-simplification,
-    # ...) that honoring USD-authored ``physics:approximation`` requires.
-    "newton[sim,importers]>=1.2.0",
+    "newton[sim]>=1.2.0",
+    # Import and mesh-processing packages used by Newton, including the ones that honoring
+    # USD-authored ``physics:approximation`` requires. Keep these explicit instead of selecting
+    # newton[importers], whose standalone USD dependency would overlap with usd-exchange.
+    "requests>=2.25.0",
+    "scipy>=1.11.0",
+    "coacd>=1.0.7",
+    "fast-simplification>=0.1.11",
+    "alphashape>=1.3.1",
+    "meshio>=5.3.5",
+    "pycollada>=0.9",
+    "resolve-robotics-uri-py>=0.4.0",
+    "open3d>=0.19.0 ; python_version < '3.13' and (sys_platform != 'linux' or platform_machine != 'aarch64')",
     # Loose bound co-resolves with isaacsim's ==0.2.0; the override below forces >=0.4.1.
     "newton-usd-schemas>=0.2.0",
     "PyOpenGL-accelerate>=3.1.0",
@@ -146,6 +160,7 @@ rerun = [
 ]
 
 isaacsim = ["isaacsim[all,extscache]==6.0.1.0"]
+
 ov = ["ovphysx==0.5.9", "ovrtx>=0.4.0,<0.5.0", "ovstage==0.1.0.346039"]
 ovphysx = ["ovphysx==0.5.9", "ovstage==0.1.0.346039"]
 ovrtx = ["ovrtx>=0.4.0,<0.5.0", "ovstage==0.1.0.346039"]
@@ -179,9 +194,9 @@ leapp = [
     "leapp>=0.5.2",
 ]
 # Every backend, RL library, and visualizer in one flag. No extra is forked in
-# [tool.uv].conflicts, so Isaac Sim and both OV backends resolve into a single
-# environment. The specialized extras (rlinf, mimic, teleop, tetrahedralization,
-# video, leapp) and the developer ``test`` tooling stay opt-in by name.
+# [tool.uv].conflicts, so any combination resolves into a single environment. The
+# specialized extras (rlinf, mimic, teleop, tetrahedralization, video, leapp)
+# and the developer ``test`` tooling stay opt-in by name.
 all = [
     "isaaclab-dev[sb3,skrl,rl-games,rsl-rl,viser,rerun,isaacsim,ov]",
 ]
@@ -192,6 +207,7 @@ all = [
 # ``test_version_single_source`` fails CI if they drift.
 [tool.isaaclab.versions]
 isaacsim = "6.0.1.0"
+usd_exchange = "2.3.0"
 torch = "2.11.0"
 torchvision = "0.26.0"
 torchaudio = "2.11.0"
@@ -335,6 +351,7 @@ markers = [
     "benchmark: test covers the Isaac Lab benchmark framework and infrastructure",
     "rendering: test exercises the rendering / camera / visualizer pipeline",
     "smoke: tests for core installation, task, and RL functionality",
+    "kitless: test must pass inside the Kit-less container, which has no Isaac Sim runtime",
 ]
 
 # Add pypi.nvidia.com so that `uv pip install isaaclab[isaacsim]` works without --extra-index-url.
@@ -380,7 +397,7 @@ override-dependencies = [
     "numpy>=2",
     "mujoco~=3.11.0",
     "mujoco-warp~=3.11.0",
-    "newton[sim,importers] @ git+https://github.com/newton-physics/newton.git@release-1.5",
+    "newton[sim] @ git+https://github.com/newton-physics/newton.git@release-1.5",
     # Force the Newton-matched schemas over isaacsim's ==0.2.0 pin.
     "newton-usd-schemas>=0.4.1",
     "torch==2.11.0",
@@ -393,10 +410,6 @@ override-dependencies = [
     # ovphysx caps packaging at <24 and isaacsim-core pins ==26.0; both caps are
     # stricter than the code needs, so widening lets them resolve together at 26.0.
     "packaging>=20,<27",
-    # usd-exchange and usd-core each vendor a full ``pxr`` built against a different
-    # USD version, and newton[importers] pulls usd-exchange unmarked. Re-impose the
-    # platform split from [project.dependencies] so only one lands per platform.
-    "usd-exchange>=2.2 ; platform_machine == 'aarch64'",
 ]
 python-preference = "only-managed"
 package = false

scripts/tools/convert_mjcf.py

@@ -36,9 +36,9 @@
 """Parse CLI first so we can decide whether to launch Isaac Sim Kit."""
 
 import argparse
-from importlib import metadata
 
 from isaaclab.app import AppLauncher, add_launcher_args, launch_simulation
+from isaaclab.utils.version import standalone_importers_available
 
 parser = argparse.ArgumentParser(description="Utility to convert a MJCF into USD format.")
 parser.add_argument("input", type=str, help="The path to the input MJCF file.")
@@ -82,14 +82,12 @@
 add_launcher_args(parser)
 args_cli = parser.parse_args()
 
-# The MJCF importer ships as a Kit extension unless the standalone importer wheel is installed, so
-# Kit is only required when the wheel is absent. With the wheel present the conversion runs kitlessly
-# and the kitless visualizers can host the preview.
-try:
-    metadata.distribution("isaacsim-asset-isolated")
-    args_cli.require_kit = False
-except metadata.PackageNotFoundError:
-    args_cli.require_kit = True
+# Prefer kit-less: it skips Kit startup and the kitless visualizers can host the preview.
+args_cli.require_kit = not standalone_importers_available()
+
+# ``launch_simulation`` receives a bare ``PhysicsCfg()`` placeholder, so name the backend the
+# runtime provides; without it the preview builds a simulation with no physics manager.
+args_cli.physics = "isaacsim_physx" if args_cli.require_kit else "newton_mjwarp"
 
 # Report the missing importer before converting anything. Without this the launcher reports only
 # that Isaac Sim is absent, which does not mention the wheel that would make this run kitlessly.

scripts/tools/convert_urdf.py

@@ -36,9 +36,9 @@
 """Parse CLI first so we can decide whether to launch Isaac Sim Kit."""
 
 import argparse
-from importlib import metadata
 
 from isaaclab.app import AppLauncher, add_launcher_args, launch_simulation
+from isaaclab.utils.version import standalone_importers_available
 
 parser = argparse.ArgumentParser(description="Utility to convert a URDF into USD format.")
 parser.add_argument("input", type=str, help="The path to the input URDF file.")
@@ -78,14 +78,12 @@
 add_launcher_args(parser)
 args_cli = parser.parse_args()
 
-# The URDF importer ships as a Kit extension unless the standalone importer wheel is installed, so
-# Kit is only required when the wheel is absent. With the wheel present the conversion runs kitlessly
-# and the kitless visualizers can host the preview.
-try:
-    metadata.distribution("isaacsim-asset-isolated")
-    args_cli.require_kit = False
-except metadata.PackageNotFoundError:
-    args_cli.require_kit = True
+# Prefer kit-less: it skips Kit startup and the kitless visualizers can host the preview.
+args_cli.require_kit = not standalone_importers_available()
+
+# ``launch_simulation`` receives a bare ``PhysicsCfg()`` placeholder, so name the backend the
+# runtime provides; without it the preview builds a simulation with no physics manager.
+args_cli.physics = "isaacsim_physx" if args_cli.require_kit else "newton_mjwarp"
 
 # Report the missing importer before converting anything. Without this the launcher reports only
 # that Isaac Sim is absent, which does not mention the wheel that would make this run kitlessly.

source/isaaclab/changelog.d/jichuanh-standalone-importers.minor.rst

@@ -0,0 +1,37 @@
+Added
+^^^^^
+
+* Added the standalone URDF and MJCF importers as base dependencies, so conversion works without
+  Isaac Sim and without an extra install step.
+
+* Added :attr:`~isaaclab.sim.converters.AssetConverterBaseCfg.physics_variant` to choose which
+  ``"Physics"`` variant the URDF and MJCF converters select.
+
+Fixed
+^^^^^
+
+* Fixed ``scripts/tools/convert_urdf.py`` and ``scripts/tools/convert_mjcf.py`` crashing when the
+  converted asset was previewed with a kitless visualizer (``--viz newton``, ``--viz rerun``, or
+  ``--viz viser``), by selecting the physics backend that matches the runtime.
+
+* Fixed URDF and MJCF conversion producing assets with no joints, articulation roots, or mass
+  properties.
+
+* Fixed MJCF conversion failing with ``Cannot find a valid schema for 'MjcSceneAPI'``.
+
+* Fixed installation failures caused by overlapping standalone USD providers by using
+  ``usd-exchange`` on all supported platforms and installing required Newton mesh-processing
+  packages directly.
+
+* Fixed :meth:`~isaaclab.utils.dict.class_to_dict` expanding enum values into their internal
+  members.
+
+Changed
+^^^^^^^
+
+* Changed :meth:`~isaaclab.sim.utils.select_usd_variants` to raise when a variant set exists on the
+  prim but does not offer the requested variant, which includes
+  :attr:`~isaaclab.sim.UsdFileCfg.variants` at spawn time. USD accepts such a selection and composes
+  the prim as if nothing were selected, so the asset used to spawn silently without what the variant
+  carries. A variant set the prim does not have is still skipped with a warning. Set a variant the
+  asset offers, or drop the entry.

source/isaaclab/isaaclab/__init__.py

@@ -6,6 +6,7 @@
 """Package containing the core framework."""
 
 import importlib.metadata
+import importlib.util
 import os
 import sys
 
@@ -79,7 +80,33 @@ def _should_demote(path: str) -> bool:
         os.environ["PYTHONPATH"] = os.pathsep.join(env_clean + env_demoted)
 
 
+def _expose_mujoco_usd_schemas():
+    """Put the MuJoCo USD schemas on OpenUSD's plugin search path.
+
+    ``mujoco-usd-converter`` ships them as a codeless schema plugin that it registers when the
+    package is imported. OpenUSD builds its schema registry once, on the first schema query, and
+    ignores plugins registered after that -- so MJCF conversion fails with "Cannot find a valid
+    schema for ``MjcSceneAPI``" whenever anything touched a schema first. Adding the plugin to the
+    search path lets OpenUSD find it while building the registry, so importing the converter late
+    no longer matters.
+
+    OpenUSD reads the search path while building the registry, so this only helps while the
+    registry is still unbuilt. A host that queries a schema before importing Isaac Lab has to put
+    the plugin directory on ``PXR_PLUGINPATH_NAME`` itself.
+    """
+    spec = importlib.util.find_spec("mujoco_usd_converter")
+    if spec is None or spec.origin is None:
+        return
+    plugins = os.path.join(os.path.dirname(spec.origin), "plugins")
+    if not os.path.isdir(plugins):
+        return
+    search_path = os.environ.get("PXR_PLUGINPATH_NAME", "")
+    if plugins not in search_path.split(os.pathsep):
+        os.environ["PXR_PLUGINPATH_NAME"] = os.pathsep.join(filter(None, (search_path, plugins)))
+
+
 _deprioritize_prebundle_paths()
+_expose_mujoco_usd_schemas()
 
 
 try:

source/isaaclab/isaaclab/benchmark/capture.py

@@ -171,6 +171,7 @@ def capture_versions(bm: Any) -> Versions:
         mujoco=md.get("mujoco_version"),
         cuda_bindings=md.get("cuda_bindings_version"),
         usd_core=md.get("usd_core_version"),
+        usd_exchange=md.get("usd_exchange_version"),
         isaaclab_release=md.get("isaaclab_release_version"),
     )
 

source/isaaclab/isaaclab/benchmark/recorders/record_version_info.py

@@ -131,7 +131,10 @@ def _get_version_info(self) -> None:
         # Key dependencies
         self._record("gymnasium", self._get_pkg_version("gymnasium"))
         self._record("cuda_bindings", self._get_pkg_version("cuda-bindings"))
+        # usd-exchange is the standalone USD provider; usd-core only appears in environments
+        # that predate the switch, so record whichever one is installed.
         self._record("usd_core", self._get_pkg_version("usd-core"))
+        self._record("usd_exchange", self._get_pkg_version("usd-exchange"))
 
         # Release version from root VERSION file
         version_file = os.path.join(_REPO_ROOT, "VERSION")